The present invention relates to an improved locking structure and, more particularly, to an improved locking structure installed in a retractable draw bar of a travelling case to facilitate the protraction/retraction and the positioning of the retractable draw bar. The retractable draw bar can be pulled upwards or pushed downwards to achieve smoother operation. Moreover, more convenient assembly of the retractable draw bar can be achieved.
For a travelling case with rollers installed at the bottom thereof, there is a retractable draw bar allocated to facilitate the protraction/retraction of a draw handle so that the draw handle can be gripped conveniently when used and occupies no space when not used. Moreover, to let the retractable draw bar be positioned at a proper position when protracted, there is a locking structure installed between a first joint tube and a second joint tube to control the retractile state of each joint tube.
With the retractable draw bar of a commercial travelling case as an example, the locking structure has a shell body, which has a top hole and two side holes disposed at two opposite sides. A longitudinally movable control element pushed by a main resilient element is inserted in the top hole. The control element has a first bevel and a second bevel spaced vertically. A first click element and a second click element respectively pushed by the first resilient element and the second resilient element and respectively protruding transversely to the first side hole and the second side hole are installed in the shell body. The two click elements are vertically spaced and have slanting parts corresponding to the first bevel and the second bevel, respectively. When the retractable draw bar is pulled upwards or pushed downwards, the first bevel of the control element can push sideward the slanting part of the first click element or the second bevel of the control element can push sideward the slanting part of the second click element so that the first click element or the second click element will be retracted from the side hole. The retractable draw bar can thus be protracted or retracted freely.
However, the design of this kind of locking structure may generate the following problems in assembly and use.
(1). The components of the locking structure comprises at least a shell body, a control element, a main resilient element, a first click element, a first resilient element, a second click element, and a second resilient element. There are a large number of components having small volumes. The shell body is formed by joining a front shell and a back shell. Moreover, there are many separate resilient elements. Therefore, assembly of the locking structure is time-consuming and laborsome.
(2). Although the first click element and the second click element of the locking structure work in reverse directions to be secured and positioned timely in the upper side hole and the lower side hole when the draw bar is pulled upwards or pushed downwards, they are spaced vertically and work independently. That is, there is no interaction between them. On one hand, this results in increase and dispersion of components. On the other hand, discord may arise between them to deteriorate smooth protraction/retraction and steady positioning of the retractable draw bar.
(3). This kind of locking structure having two click elements is mainly used in each draw bar except the first draw bar and is pushed downwards to work. Another simplified locking structure having only a click element must be used in the first draw bar. This simplified locking structure is also pushed downwards to work. Another working way of pulling upwards via a steel cord can not be used, resulting in limited use.
One object of the present invention is to provide an improved locking structure of a retractable draw bar, wherein the number of components thereof is reduced and there are higher compatibility and interaction between them. Easy assembly and smooth protraction/retraction and steady positioning of the retractable draw bar can thus be achieved.
Another object of the present invention is to provide an improved locking structure of a retractable draw bar, which not only can be widely used between any two draw bars of a retractable draw bar, but also applies to both the upward-pull type and the downward-push type retractable draw bars.
To achieve the above objects, a locking mechanism of the present invention comprises a fixed assembly, a movable assembly, an upper click button, a lower click button, and two resilient elements. The movable assembly is inserted in the fixed assembly and can steadily move upwards or downwards with respect to the fixed assembly. The upper click button, the first resilient element, the lower click button, and the second resilient element are axially adjacent and are installed in a transverse allocation hole of the fixed assembly so that the upper click button penetrates in the movable assembly. The upper and lower click buttons can thus work in opposite directions. A wedged guide groove and a wedged guide block both having an upper bevel and a lower bevel are installed at corresponding positions on the movable assembly and the upper click button, respectively. No matter the movable assembly is pulled upwards or pushed downwards, the upper click button can be pushed sideward and retracted transversely from the click hole.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawings, in which: